Field of the Invention
The present invention relates generally to surgical instruments and systems, and more particularly to surgical instruments with low backlash drive systems.
Description of Related Art
Robotically controlled systems such as employed for minimally invasive medical procedures can include large and complex equipment to precisely control and drive relatively small tools or instruments. (As used herein, the terms “robot” or “robotically” and the like include teleoperation or telerobotic aspects.) FIG. 1A illustrates an example of a known robotically controlled system 100. System 100, which may, for example, be part of a da Vinci® Surgical System commercialized by Intuitive Surgical, Inc., includes a patient-side cart 110 having multiple arms 130. Each arm 130 has a docking port 140 that generally includes a drive system with a mechanical interface for mounting and providing mechanical power for operation of an instrument 150. Arms 130 can be used during a medical procedure to move and position respective medical instruments 150 for the procedure.
FIG. 1B shows a bottom view of a known instrument 150. Instrument 150 generally includes a transmission or backend mechanism 152, a main tube 154 extending from the backend mechanism 152, and a functional tip 156 at the distal end of the main tube 154. Tip 156 generally includes a medical tool such as a scalpel, scissors, forceps, or a cauterizing instrument that can be used during a medical procedure. Drive cables or tendons 155 connected to tip 156 and extend through main tube 154 to backend mechanism 152. Backend mechanism 152 typically provides a mechanical coupling between the drive tendons of the instrument 150 and motorized axes of the mechanical interface of a drive system 140. In particular, gears or disks 153 have features such as projections or holes that are positioned, sized, and shaped to engage complementary features on the mechanical interface of a drive system 140. In a typical instrument, rotation of disks 153 pulls on respective tendons 155 and actuates corresponding mechanical links in tip 156. System 100 can thus control movement and tension in drive tendons 155 as needed to position, orient, and operate tip 156. Further details of known surgical systems are described, for example, in U.S. Pat. No. 7,048,745 (filed Aug. 13, 2001) to Tierney et al., entitled “Surgical Robotic Tools, Data Architecture, and Use,” which is hereby incorporated by reference in its entirety.
Instruments 150 of system 100 can be interchanged by removing one instrument 150 from a drive system 140 and then installing another instrument 150 in place of the instrument removed. The installation process in general requires that the features on disks 153 properly engage complementary features of drive system 140. However, before installation, the orientations of disks 153 on instrument 150 are generally unknown to patient-side cart 110.
Further, equipment such as patient-side cart 110 is often covered for a medical procedure by a sterile barrier (e.g., a plastic sheet drape) because of the difficulty in cleaning and sterilizing complex equipment between medical procedures. This sterile barrier can include a sterile adaptor that is interposed between docking port 140 and instrument backend 152. See for example, U.S. Pat. No. 7,048,745 and U.S. Pat. No. 7,699,855 (filed Mar. 31, 2006) to Anderson et al., entitled “Sterile Surgical Adaptor”, which is hereby incorporated by reference in its entirety, describe some exemplary sterile barrier and adaptor systems.
A typical installation process for an instrument 150 involves mounting backend mechanism 152 without regard for the orientations of disks 153 on a drive system 140, possibly with an intervening sterile adaptor. The drive motors in drive system 140 may be then be rotated back and forth multiple times during the installation procedure to ensure that the complementary features mesh with and securely engage each other for operation of the newly installed instrument 150. At some point during the installation process, the drive motors become securely engaged to rotate respective disks 153. However, the instrument 150 being installed may move in an unpredictable manner at times during the installation procedure because the drive motors positively engage respective disks 153 of instrument 150 at different and unpredictable times. For certain applications, such unpredictable motion is unacceptable. In general, clear or confined space is required around an instrument 150 to accommodate random movements of the instrument tip during an installation procedure.